The present invention generally relates to compositions useful for therapeutic applications, and, more specifically, to compositions and methods of use of such compositions for bone tissue regeneration.
Bone tissue regeneration to repair bone defects, whether they are the result of injury, surgery, disease, or old-age, has been a common goal of medicine and dentistry. The procedure has seen more recent widespread application in the dental field due to the popularity of dental implants. Conventionally, bone tissue regeneration can be achieved by filling a bone defect site (recipient graft site) with graft material and covering the graft material with a barrier material to exclude competitive cells.
The nature of the graft material used determines how bone tissue is regenerated. If live active bone tissue is used as the graft material, it carries with it osteoblasts that form new bone. In addition, the live active bone tissue induces undifferentiated cells in the recipient graft site to differentiate into osteoblasts that further form new bone. Fresh autogenous cancellous bone and marrow is an example of live active bone tissue that can be used as a graft material. Demineralized, freeze-dried, allogenic bone ("DFDBA"), an inducing graft material, has also been used as a graft material. It induces undifferentiated cells in the graft site to differentiate into osteoblasts and grow into new bone, while the graft material is resorbed by the host. Finally, autogenous cortical bone chips, a scaffolding type graft material, has been used. The scaffolding type graft material passively attracts osteoblasts native to the recipient graft site in the scaffolding, where the cells may grow into new bone.
Although graft materials of the type that contain live active bone tissue produce excellent bone tissue regeneration, such materials require extraction of live tissue from a donor. If the donor is the same individual requiring bone tissue regeneration, such live tissue is in limited supply. Moreover, the remaining conventional graft materials do not always provide reliable bone tissue regeneration because they are not capable of inducing sufficient recipient graft site bone formation before competitive soft tissue and epithelial cells fill the recipient graft site.
The barrier material has functioned as a physical barrier to protect the graft material from disruption, to retard the ingrowth of unwanted tissue into the graft material and to allow cells to migrate into the recipient graft site from adjacent osseous tissues. To date the most popular barrier material has been a poly-tetrafluorethylene membrane (PTFE) even though there are many problems associated with its use. First, PTFE is not biodegradable. Therefore, it has been necessary to perform a second operation to remove the PTFE barrier. In addition, infection is likely to occur particularly if complete soft tissue coverage cannot be obtained. If the PTFE barrier is exposed, the patient can be uncomfortable until it is removed, sometime between four to six weeks. Since PTFE is generally used in a solid form and graft recipient sites have a variety of shapes and grooves, the PTFE barrier material must be trimmed during surgery to conform to the graft recipient site and then sutured in place. This procedure can be time consuming particularly if multiple defects exist.
Accordingly, a need exists for a composition that can be used to regenerate bone tissue in a reliable manner without undue risk of infection and without the need for prolonged and multiple operative procedures. The compositions of the present invention meet these needs and provides related advantages as well.